Process for manufacturing a multi-layer lead frame

ABSTRACT

A process for manufacturing a multi-layer lead frame for a semiconductor device comprises two metal plains being adhered to each other via an insulation piece. An insulation strip is punched to cut the insulation piece, which is preliminary adhered to a metal strip. The metal strip is then punched to cut and remove the metal plane, which is then laminated and heat-pressed to another metal strip. After completely adhered, the other metal strip is punched to remove a multi-layer lead frame.

This application is a continuation of application Ser. No. 701,182,filed May 16, 1991, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for manufacturing a lead frame, moreparticularly to a process for manufacturing a multi-layer lead framehaving at least one metal plate or plane, hereinafter referred to as"metal plane" which is used for a semiconductor device.

2. Related Art

A plastic package, whose speed and heat-radiation characteristics are asgood as those of a ceramic package, has recently been developed. Inaddition, in place of a conventional single-layer lead frame, amulti-layer plastic lead frame for a semiconductor device has also beendeveloped.

Such a multi-layer lead frame comprises at least one metal planeconnected via an insulative layer to the bottom surfaces of inner leads.Using such a multi-layer lead frame, it will be possible to mount arelatively power-consumable semiconductor chip on the metal plane, dueto a good heat radiation capacity of the metal plane. Also, the metalplane can be used as a ground layer or a power supply layer to improvethe electrical characteristics of the semiconductor device.

FIG. 10 shows a conventionally known multi-layer lead frame whichcomprises three layers, i.e., a signal layer (i.e., lead frame 12) andtwo metal planes. i.e., a power supply metal plane 20 and a ground metalplane 62, which are laminated via insulative tapes 42a and 17b made ofheat-resistant material including, such as a polyimide.

Using such a multi-layer lead frame, it would be possible to prevent aso-called cross talk which might be generated between signal lines andalso possible to reduce the capacitance between the lines or inductance.

As shown in FIG. 10, in order to manufacture the above-mentionedmulti-layer lead frame, at the first stage, a lead frame 12, a powersupplying metal plane 20, a ground metal plane 62, and insulative tapepieces 42a and 42b each having respective surfaces providing withadhesive layers must individually be made. Then, these individual piecesmust be positioned by using a special instrument, such as an imagereader (not shown), and then heat-pressed to laminate and adhere themtogether.

However, in the above mentioned manufacturing process, it has been verytroublesome and laborious work to position and laminate the five layersincluding the insulative tape pieces 42a and 42b by using the imagereader. It also requires a lot of time and, therefore, an effectiveproduction rate would not be expected. In addition, when these piecesare released or disengaged from the gripping means after the pieces aregripped by the gripping means and laminated, the laminated pieces mightbe moved slightly and, therefore, a precise laminated multi-layer leadframe might not be obtained.

The multi-layer lead frame should originally have a good quality formulti-pin and, therefore, inner leads thereof are usually very dense.Thus, even a slight aberration might cause a disconnection between theterminals of the power supply plane 20 or the ground plane 32 and thecorresponding inner leads of the lead frame 10.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a process formanufacturing a multi-layer lead frame, in which the lead frame base orthe metal planes can be precisely and effectively positioned.

According to this invention, there is provided a process formanufacturing a multi-layer lead frame for a semiconductor devicecomprising a lead frame body and at least one metal plane adhered tolead frame body by means of an insulation tape piece, said processcomprising the following steps of: forming a lead frame strip and atleast one metal plane strip from metal strips, said lead frame stripcomprising a plurality of said lead frame bases longitudinally andcontinuously arranged, said metal plane strip comprising a plurality ofsaid metal planes longitudinally and continuously arranged and connectedto a second supporting frame via second connecting portions, and each ofsaid first and second supporting frames having positioning means, suchas, guide holes; forming at least one insulation tape strip from a resinstrip providing adhesive layers on its respective surfaces, saidinsulation tape strip comprising a plurality of said insulation tapepieces longitudinally and continuously arranged and connected to a thirdsupporting frame via third connecting portions, said third supportingframe having positioning means, such as, guide holes; positioning saidinsulation tape strip with respect to said metal plane strip by theirpositioning means; punching said insulation tape strip to cut and removeat least one of said the insulation tape pieces from said thirdconnecting portions and preliminary adhering said insulation tape pieceto at least one of said metal planes of said metal plane strip;positioning said metal plane strip with respect to said lead framestrip; punching said metal plane strip to cut and remove said at leastone metal plane from said second connecting portions and laminating saidmetal plane to heat-press and completely adhere it to said at least onelead frame base of said lead frame strip; and punching said lead framestrip to cut and remove said at least one lead frame from said firstconnecting portions and separate it from its supporting frame.

Thus, according to the present invention, the lead frame base or themetal planes can be precisely and effectively positioned, since thepositioning of the lead frame strip and the metal plane strip can beeasily and precisely performed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a manufacturing process of themulti-layerd lead frame;

FIGS. 2, 3, 4 and 5 are plan views of the lead frame strip, the powersupply plane, the ground plane, and the insulation tape strip,respectively;

FIGS. 6, 7, 8 and 9 are schematic cross-sectional views of heat pressingdevices; and,

FIG. 10 is an exploded view of a multi-layer lead frame known in theprior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, FIGS. 1-8 show a preferred embodiment ofa process for manufacturing a multi-layer lead frame according to thepresent invention.

A multi-layer lead frame can be manufactured by a process as describedbelow with reference to FIG. 1, in which, A is a line of process formanufacturing a lead frame strip 10, B is a line of process formanufacturing a power supply plane strip 18, and C is a line of processfor manufacturing a ground plane strip 30. D and E are also lines ofprocess for providing insulation tapes.

In the process line A, a metal strip 10 is forwardly fed through severalmetal molds (not shown). Along these molds the lead frame strip 10 isformed in a conventionally known manner. Thus, as schematically shown inFIG. 2, obtained is a lead frame strip 10 comprising a support frame 14and a plurality of lead frames 12 longitudinally and continuouslyarranged and connected to each other by means of connecting portions.The support frame 14 is provided with a plurality of regularly arrangedguide holes 16 which cooperate with guide means (not shown) for feedingthis lead frame strip 10 forwardly through the metal molds.

The process line B intersects perpendicularly with the process line A ata position A1 downstream of the working stations for entirely formingall of the patterns of the lead frame strip 10. In the process line B,another metal strip is fed forwardly through several metal molds (notshown) to form a power supply plane strip 18 which comprises, as shownin FIG. 3, a plurality of power supply planes 20 longitudinally andcontinuously arranged and connected to a supporting frame 24 by means ofconnecting portions 22. A reference numeral 26 indicates terminals whichare protruded from the power supply plane 20. Such terminals 26 areconnected to predetermined power supply leads of the lead frame 12 whenthe power supply plane 20 is laminated to the lead frame 12. A referencenumeral 28 indicates positioning guide holes which are used for feedingthe power supply plane strip 18 through the metal molds, as mentionedabove.

The process line C also intersects perpendicularly with the process lineA at a position A2 downstream of the intersection with the process lineB. In the same manner as the above, in the process line C, a stillanother metal strip is fed forwardly through several metal molds (notshown) to form a ground plane strip 30 which comprises, as shown in FIG.4, a plurality of ground planes 32 longitudinally and continuouslyarranged and connected to a supporting frame 36 by means of connectingportions 34. A reference numeral 38 indicates terminals which areprotruded from the ground plane 32. Such terminals 38 are connected topredetermined ground leads of the lead frame 10, when the ground plane32 is laminated to the lead frame 10. A reference numeral 39 indicatespositioning guide holes which are used for feeding the ground planestrip 30 through the metal molds, as mentioned above.

The process line D for forming a first insulation tape strip 40 isarranged to intersect perpendicularly with the process line B at aposition downstream of a final step for forming the power supply planestrip 18 in the process line B.

In this process line D, a resin strip is fed forwardly through severalmetal molds (not shown) to form a frame-like insulation tape strip 40which comprises, as shown in FIG. 5, a plurality of insulation tapepieces 42 longitudinally and continuously arranged and connected to asupporting frame 46 by means of connecting portions 44. Such aninsulation tape piece 42 is used for adhering the lead frame 12 to thepower supply plane 20. A reference numeral 48 indicates guide holes. Theabove-mentioned insulation tape strip 40 may be a so-called double sidedadhesive tape comprising a heat-resistant resin sheet made of, such as,a polyimide and having respective surfaces to which suitable resin pastecomprising, such as, a thermosetting resin contained in any solutionmedia is coated and dried to form adhesive layers.

The insulation tape piece 42 of the first insulation tape strip 40 iscut from the connecting portion 44 at the intersection of the processline B and provisionally adhered to the bottom surface of the powersupply plane 20 (strip 18) at a predetermined position.

FIG. 6 shows an example of the heat press apparatus which comprises acutting punch 50, a die 51, and a heater block 52. When the insulationtape strip 40 is positioned by means of the above-mentioned guide holes48 and fed to a predetermined position between the cutting punch 50 andthe die 51, the cutting punch 50 is moved upward to cut the connectingportions 44, so that the insulation tape strip 40 is cut into theindividual insulation tape piece 42, which is then heat-pressed againstthe power supply plane 20 (strip 18) provisionally heated by the heaterblock 52. The heat-pressing in this process is conducted at thetemperature of, such as 180° C., which is sufficient to soften theadhesion of the insulation tape piece 42 to be adherent, but not tocompletely harden the thermosetting adhesive.

After the insulation tape pieces 42 are removed from the insulation tapestrip 40, the supporting frame 46 is wound onto an appropriate reel (notshown).

The pressing surface of the cutting punch 50 may be provided with somesuction holes communicated to any vacuume means (not shown) for suckingto hold the cut insulation tape piece 42 and simultaneously to press thesame against the power supply plane 20 (strip 18). Thus, the insulationtape piece 42 is held stably against the power supply plane 20 (strip18).

The process line E for forming a second insulation tape strip 40 isarranged to intersect perpendicularly with the process line C at aposition downstream of a final step for forming the ground plane strip30 in the process line C. In this process line E, a resin strip is fedforwardly through several metal molds (not shown) to form a frame-likeinsulation tape strip 40 in the same manner as the above. Thus, theinsulation tape piece 42 is used for preliminary adhering the groundplane 32 to the power supply plane 20.

The the second insulation tape strip 40 is cut from the connectingportion 44 into the insulation tape piece 42 at the intersection of theprocess line C. The insulation tape piece 42 is provisionally adhered tothe bottom surface of the ground plane 32 at a predetermined position.

After the first and second insulation tape strips 40 are cut into theindividual insulation tape pieces 42 and heat-pressed against the powersupply plane 20 (strip 18) and the ground plane 32 (strip 30),respectively, the lattters are then further fed to the intersectionswith the process line A.

FIG. 7 shows an example of a heat press apparatus which is substantiallythe same as that shown in FIG. 6, except that the cutting punch 50 isarranged upside and the die 51 and the heater block 52 are arrangeddownside. When the power supply strip plane 18, to which the insulationtape piece 42 is preliminary adhered, is positioned by means of theabove-mentioned guide holes 28 and fed to a predetermined position A1(FIG. 1) between the cutting punch 50 and the die 51, the cutting punch50 is moved downward to cut the connecting portions 22, so that thepower supply plane strip 18 is cut into the individual power supplystrip which is then heat-pressed against lead frame 12 provisionallyheated by the heater block 52.

Thus, the lead frame strip 10, to which the power supply plane 20adhered by means of the insulation tape piece 42, is further fedforwardly and, at the intersection A2 (FIG. 1) of the process line C,the ground plane 32, to which the first insulation tape piece 42 isprovisionally adhered, is then provisionally adhered to the power supplyplane 20 by means of the second insulation tape piece 42, in the samemanner as mentioned above. That is to say, as shown in FIG. 8, when thelead frame strip 10 and the ground plane strip 30 are positioned to eachother by means of the respective guide holes and fed forwardly to theintersection A2 of the process line C, the cutting punch 50 is loweredto cut the ground plane strip 30 from the connecting portions 34 intothe individual ground plane 32, which is then heat-pressed against thepower supply plane 20 on the lead frame strip 10 provisionally heated bythe heater block 52 to soften the adhesive of the insulation tape piece42 to preliminary adhere the ground plane 32 against the power supplyplane 20.

Thus, the lead frame 12, to which the power supply plane 20 and theground plane strip 32 are laminated, is further fed forwardly along theprocess line A and is further heated and pressed by upper and lowerheater blocks 54a and 54b. Thus, the adhesive tapes or layers of theinsulation tape pieces 42 are suitably thermoset and, therefore, astable main or complete adhering is thus conducted.

The respective terminals of the power supply plane 20 and the groundplane strip 32 are connected to the corresponding leads of the leadframe 12 by a spot welding or the like.

According to the above-mentioned embodiment, by synchronizing operatingthe respective process lines A, B, C, D and E, the lead frame 12, thefirst and second insulation tape pieces 42, the power supply plane 20and the ground plane 32 can automatically be formed. Also, theprovisional adhering, the heat-pressing and the positioning of theinsulation tape pieces 42 can automatically be conducted. A multi-layerlead frame of this invention can thus be automatically manufacturedthroughout the whole steps.

However, such a synchronizing operation can be partly conducted. Forexample, tile operations for forming and heat-pressing of the powersupply plane strip 18 and the first insulation tape 42 are synchronizedto each other and, on the other hand, the operations for forming andheat-pressing of the ground plane strip 30 and the second insulationtape 42 are synchronized to each other. Laminating and heat-pressing ofthe power supply plane 20, to which the insulation tape 42 is attached,the ground plane 32, and the lead frame strip 10 can be synchronizingoperated as mentioned above in a separate process.

FIG. 9 shows another embodiment of a laminating process. In thisembodiment, the power supply plane strip 18, to which the firstinsulation tape pieces 42 are adhered, and the ground plane 32, to whichthe second insulation tape pieces 42 are adhered, are not cut intoindividual planes. But these strips 18 and 30 are themselves positionedby any positioning means, such as pilot pins, and superimposed on thelead frame strip 10, so that they are heat-pressed together by means ofupper and lower heater blocks 56 and 56 to thermoset the adhesive tapelayers of the first and second insulation tape pieces 42. The powersupply plane strip 18 and the ground plane strip 30 are thereafter cutinto individual planes 20 and 32 from the frame portions thereof. Theconnecting portions 22 and 34 may be provided at the bases thereof withV-shaped notches or the like extending to the direction of thickness soas to make it easy to cut the connecting portions.

In this embodiment, the first insulation tape piece 42 for adhering thepower supply plane 20 to the lead frame 12 may be provisionally adheredto the lead frame strip 10. On the other hand, the second insulationtape piece 42 for adhering the ground plane 32 to the power supply plane20 may be provisionally adhered to the power supply plane strip 18.

Although, in the above mentioned embodiments, a multi-layer lead framecomprises three layers, i.e., the lead frame, the power supply plane andthe ground plane, this invention is also applicable to any othermulti-layer lead frames comprising, such as, two layers, i.e., a leadframe and a metal plane. In this case, the metal plane may be a powersupply plane, a ground plane, or a radiation/stage plane which is notelectrically connected to the lead frame.

A multi-layer lead frame thus obtained according to the presentinvention may, of course, be comprised of four or more layers.

It should be understood by those skilled in the art that the foregoingdescription relates to only preferred embodiments of the disclosedinvention and that various changes and modifications may be made in theinvention without departing form the spirit and scope thereof.

We claim:
 1. A process for manufacturing a multi-layer lead frame for asemiconductor device comprising a lead frame body and at least one metalplane adhered to said lead frame body by means of an insulation tapepiece, said process comprising the following steps of:forming a leadframe strip and at least one metal plane strip from metal strips, saidlead frame strip comprising, a first supporting frame and a plurality oflead frame base longitudinally and continuously arranged, said metalplane strip comprising a plurality of said metal planes longitudinallyand continuously arranged and connected to each other by connectingportions, and supported by said first supporting frame and havingpositioning means; forming at least one insulation tape strip from aresin strip providing adhesive layers on its respective surfaces, saidinsulation tape strip comprising a plurality of said insulation tapepieces longitudinally and continuously arranged and connected to anothersupporting frame via other connecting portions, said other supportingframe having positioning means; positioning said insulation tape stripwith respect to said metal plane strip by their positioning means;punching said insulation tape strip to cut and remove at least one ofsaid insulation tape pieces from said other connecting portions andprovisionally adhering said insulation tape piece to at least one ofsaid metal planes of said metal plane strip; positioning said metalplane strip with respect to said lead frame strip; and punching saidmetal plane strip to cut and remove said at least one metal plane fromsaid connecting portions and laminating by heat-pressing in order tocompletely adhere to said metal plane to said at least one lead framebase of said lead frame strip.
 2. A process as set forth in cIaim 1,wherein said metal plane comprises two layers consisting of a powersupply plane and a ground plane.
 3. A process as set forth in claim 2further comprising the steps of:punching a first insulation tape stripto cut and remove at least one of first insulation tape pieces andprovisionally adhering said first insulation tape piece to at least onepower supply plane of a power supply plane strip; and, punching a secondinsulation tape strip to cut and remove at least one of secondinsulation tape pieces and provisionally adhering said second insulationtape piece to at least one ground plane of the ground plane strip.
 4. Aprocess as set forth in claim 3 further comprising the steps of:punchingsaid power supply plane strip to cut and remove said at least one powersupply plane and laminating by heating-pressing said power supply planeto provisionally adhere said power supply plane to said at least onelead frame base of said lead frame strip; and punching said ground planestrip to cut and remove said at least one ground plane and laminating byheat-pressing said ground plane to said power supply plane alreadyadhered to said lead frame base in order to adhere said ground plane tosaid power supply plane and said lead frame base.
 5. A process as inclaim 1 wherein said positioning means comprises guide holes.
 6. Aprocess for manufacturing a multi-layer lead frame for a semiconductordevice comprising a lead frame body and at least one metal plane adheredto said lead frame body by means of an insulation tape piece, saidprocess comprising the following steps of:forming a lead frame strip andat least one metal plane strip from metal strips, said lead frame stripcomprising a plurality of lead frame bases longitudinally andcontinuously arranged, said metal plane strip comprising a plurality ofsaid metal planes longitudinally and continuously arranged and connectedto a supporting frame via connecting portions, and said supporting framehaving positioning means: forming insulation tape strips from resinstrips each providing adhesive layers on its respective surfaces, eachof said insulation tape strips comprising a plurality of said insulationtape pieces longitudinally arranged and continuously connected toanother supporting frame via other connecting portions, said othersupporting frame having positioning means: positioning said lead framestrip, said metal plane strip, and said insulation tape strips,respectively, by said positioning means; punching said insulation tapestrips to cut and remove the insulation tape pieces from said anotherconnecting portions and provisionally adhering said insulation tapepieces to predetermined positions of said lead frame strip and/or saidmetal plane strip; positioning and laminating by heat-pressing said leadframe strip and said metal plane strip to completely adhere themtogether via said insulation tape pieces; and separating said metalplanes from their supporting frames.
 7. A process as set forth in claim6, wherein said metal plane comprises two layers consisting of a powersupply plane and a ground plane, and said lead frame body, said powersupply plane and said ground plane are laminated in this order.
 8. Aprocess in claim 6 wherein said positioning means comprises guide holes.9. A process for manufacturing a multi-layer lead frame for asemiconductor device comprising at least two metal planes adhered toeach other by means of an insulation tape piece, said process comprisingthe following steps of:forming at least two metal strips each comprisinga plurality of said metal planes longitudinally and continuouslyarranged and having positioning means; forming at least one insulationtape strip providing adhesive layers on its respective surfaces, saidinsulation tape strip comprising a plurality of said insulation tapepieces longitudinally and continuously arranged an having positioningmeans; positioning said insulation tape strip with respect to a firstmetal plane strip by their positioning means; punching said insulationtape strip to cut and remove said insulation tape piece andprovisionally adhering said insulation tape piece to said first metalplane strip; positioning said first metal plane strip with respect to asecond metal plane strip; punching said first metal plane strip to cutand remove a first metal plane and laminating by heat-pressing tocompletely adhere said first metal plane to said second metal planestrip; and, punching said second metal plane strip to cut and remove asecond metal plane.
 10. A process as in claim 9 wherein said positioningmeans comprises guide holes.
 11. A process for manufacturing amulti-layer lead frame for a semiconductor device comprising at leasttwo metal planes adhered to each other by means of an insulation tapepiece, said process comprising the following steps of:forming at leasttwo metal strips each comprising a plurality of said metal planeslongitudinally and continuously arranged and having positioning means;forming at least one insulation tape strip providing adhesive layers onis respective surfaces, said insulation tape strip comprising aplurality of said insulation tape pieces longitudinally and continuouslyarranged and having positioning means; positioning said insulation tapestrip with respect to a first metal plane strip by their positioningmeans; punching said insulation tape strip to cut and remove saidinsulation tape piece and provisionally adhering said insulation tapepiece to said first metal plane strip; positioning said first metalplane strip with respect to a second metal plane strip; and, laminatingby heat-pressing said first metal plane strip to said second metal planestrip to completely adhere them to each other.
 12. A process as in claim11 wherein said positioning means comprises guide holes.